Image forming apparatus and power control method thereof

ABSTRACT

An image forming apparatus and a power control method thereof are provided. The image forming apparatus includes: an image forming unit which forms an image; a power supply which supplies operating power for the image forming apparatus; a switching circuit unit which switches to selectively supply the operating power; a memory unit which stores information about power status of the switching circuit unit; and a controller which outputs a power control signal for controlling a switching operation of the switching circuit unit in accordance with the information about the power status stored in the memory unit if power is abnormally shut off and then supplied again from the power supply to the switching circuit unit. With this, the image forming apparatus operates in a last power status, so that power can be prevented from being wastefully consumed or data can be prevented from being lost.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit from Korean Patent ApplicationNo. 10-2010-0116746, filed on Nov. 23, 2010 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND

1. Field

Exemplary embodiments relate to an image forming apparatus and a powercontrol method thereof, and more particularly, to an image formingapparatus, power of which is controlled by turning on/off direct current(DC) power of a secondary circuit, and a power control method thereof.

2. Description of the Related Art

An image forming apparatus forms an image to be printed on a printingmedium. The image forming apparatus may be embodied in a printer, a copymachine, a facsimile, a multi-function peripheral having two or morefunctions, etc.

For power control of the image forming apparatus, there may be used amethod of preparing a mechanical switch at one side of the image formingapparatus and completely shutting off operating power supplied foroperation.

However, in the case where a method of turning on/off alternatingcurrent (AC) power of a primary circuit is used, an AC harness of apower inlet generally placed in a back side of the image formingapparatus has to be connected to a front side in order to place theswitch in a front side of the image forming apparatus for a user'sconvenience in operating the switch. This causes problems in designingthe apparatus and increases production costs.

Also, because the mechanical switch is turned on/off by a userregardless of operations such a printing, data transmission/reception,data storage, etc. of the image forming apparatus, damage may occur. Forexample, if the switch is turned off while the printing or the like jobis performed, data may be abnormally (improperly or incorrectly) backedup and thus lost, or a logic circuit or the like inner parts of theimage forming apparatus may be damaged.

Thus, there may be employed a method of controlling the DC power througha secondary circuit provided with a small capacity switching device suchas a transistor (e.g., field effect transistor (FET).

Since the above method of switching on/off the DC power of the secondarycircuit uses the small capacity device, it is possible to keep a standbypower of 1 watt (1 W) or less in an off status. Thus, the data backup isnormally achieved even when the switch is turned off, thereby preventingthe data from loss or the parts from damage. Accordingly, the method ofswitching on/off the DC power of the secondary circuit has widelyspread. Further, both the primary circuit and the secondary circuit maybe used.

Although it is possible to protect data from loss due to the powerswitch off through the method of turning on/off the secondary circuit,there is still a problem in that data may be lost because the databackup operation is not implemented in the case of unexpected power-offsuch as a power failure.

Also, when power supplying is resumed after the unexpected (abnormal)power-off due to the power failure, switch operation of the primarycircuit, etc. is terminated, and the image forming apparatus is forciblyturned on or off on the basis of preset information since it has noinformation about a previous power status.

Accordingly, if the image forming apparatus is previously set up to beturned on, power is supplied to the image forming apparatus and thuswastefully consumed. On the other hand, if the image forming apparatusis previously set up to be turned off, printing data received before theunexpected power-off and being on standby, fax data being received, orthe like may be lost and it is thus inconvenient for a user.

For the convenience in power control, an additional microcomputer(MICOM) may be used, but the use of the MICOM costs a great deal.

SUMMARY

Accordingly, one or more exemplary embodiments provide an image formingapparatus and a power control method thereof, in which if the imageforming apparatus is turned off by unexpected power-off such as a powerfailure and then resumed, a power status previously stored just beforethe power-off is ascertained to make the image forming apparatus operatein a last power status, thereby preventing power from being wastefullyconsumed or data from being lost.

Another exemplary embodiment is to provide an image forming apparatusand a power control method thereof, in which a microcomputer (MICOM) isnot additionally needed for power control, thereby saving costs onproduction.

Still another exemplary embodiment is to provide an image formingapparatus and a power control method thereof, in which the stability ofthe image forming apparatus can be more enhanced while keeping a standbypower of 1 W or less irrespective of presence of a mechanical switch.

According to an aspect of one or more embodiments, there is provided animage forming apparatus including: an image forming unit which forms animage; a power supply which supplies operating power for the imageforming apparatus; a switching circuit unit which switches toselectively supply the operating power; a memory unit which storesinformation about power status of the switching circuit unit; and acontroller which outputs a power control signal to control a switchingoperation of the switching circuit unit in accordance with theinformation about the power status stored in the memory unit if power isabnormally shut off and then supplied again from the power supply to theswitching circuit unit.

The image forming apparatus may further include a key input unit throughwhich a user input related to supply of the operating power is received,wherein the switching circuit unit includes a first switch turned on inresponse to the user input into the key input unit, and a second switchturned on/off in response to a power control signal of the controller,and the controller reads the information about the power status from thememory unit and outputs the power control signal for turning on/off thesecond switch to match with the read information about the power statusif power is supplied to the switching circuit unit without a user inputto the first switch.

The controller may initialize the image forming apparatus and monitorthe user input to the first switch if the read information about thepower status is “on”.

The controller may record the power status of the switching circuit unitas “off” in the memory unit and control the switching circuit unit toshut off the operating power if the user input to the first switch isreceived.

The controller may back up data of the image forming apparatus, andcontrol the switching circuit unit to shut off the operating power.

The controller may output a power control signal for turning off theswitching circuit unit if the read information about the power status is“off”.

The controller may record the power status of the switching circuit unitas “on” in the memory unit if power is supplied to the switching circuitby the user input to the first switch.

The controller may initialize the image forming apparatus, and monitorthe user input to the first switch.

The controller may record the power status of the switching circuit unitas “off” in the memory unit if receiving the user input to the firstswitch, and control the switching circuit unit to shut off the operatingpower.

The controller may back up data of the image forming apparatus, andcontrol the switching circuit unit to shut off the operating power.

The memory unit may include a non-volatile memory.

According an aspect of one or more embodiments, there is provided apower control method of an image forming apparatus including a powersupply for supplying operating power, and a switching circuit unit forswitching to selectively supply the operating power, the power controlmethod including: supplying power from the power supply to the switchingcircuit unit; reading information about power status from a memory unitstoring information about power status of the switching circuit unit ifpower is abnormally shut off and then supplied again to the switchingcircuit unit; and outputting a power control signal for controlling aswitching operation of the switching circuit unit in response to theread information about the power status.

The switching circuit unit may include a first switch turned on inresponse to a user input related to supply of the operating power, and asecond switch turned on/off in response to the power control signal ofthe controller, and if power is supplied to the switching circuit unitwithout a user input to the first switch, the outputting of the powercontrol signal may include outputting a power control signal for turningon/off the second switch to match with the read information about thepower status.

The power control method may further include initializing the imageforming apparatus; and monitoring a user input to the first switch, ifthe read information about the power status is “on”.

The power control method may further include receiving the user input tothe first switch; recording the power status of the switching circuitunit as “off” in the memory unit; and outputting the power controlsignal to shut off the operating power.

The power control method may further include backing up data of theimage forming apparatus.

The outputting of the power control signal may include outputting thepower control signal for turning off the switching circuit unit if theread information about the power status is “off”.

The power control method may further include recording the power statusof the switching circuit unit as “on” in the memory unit if power issupplied to the switching circuit unit by the user input to the firstswitch.

The power control method may further include initializing the imageforming apparatus; and monitoring the user input to the first switch.

The power control method may further include recording the power statusof the switching circuit unit as “off” in the memory unit if receivingthe user input to the first switch to shut off the operation power as amonitoring result; and controlling the switching circuit unit to shutoff the operating power.

The power control method may further include backing up data of theimage forming apparatus.

The memory unit may include a non-volatile memory.

Still another aspect may be achieved by providing a power control methodof an image forming apparatus including a power supply to supplyoperating power, a key input unit for receiving a user input related tosupply of the operating power, and a switching circuit unit forswitching to selectively supply the operating power, the power controlmethod including: supplying power from the power supply to the switchingcircuit unit; recording a power status of the switching circuit unit as“on” in the memory unit if power is supplied to the switching circuitunit because the key input unit receives the user input requesting thatpower be supplied from the power supply to the switching circuit unit;and initializing the image forming apparatus.

The power control method may further include supplying power to acontroller as the power is supplied to the switching circuit unit, andbooting up the controller, wherein the image forming apparatus isinitialized by the booted-up controller.

The power control method may further include monitoring the user unit tothe key input unit; recording the power status of the switching circuitunit as “off” in the memory unit if receiving the user input to thefirst switch to the switching circuit unit because as a monitoringresult; and outputting the power control signal to shut off theoperating power.

The power control method may further include backing up data of theimage forming apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of exemplary embodiments,taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram showing a configuration of an image formingapparatus according to an exemplary embodiment;

FIG. 2 is a circuit diagram of a switching circuit unit according to anexemplary embodiment;

FIG. 3 shows an example of a key input unit provided in the imageforming apparatus according to an exemplary embodiment;

FIGS. 4 and 5 are graphs showing operation waveforms detected in eachnode of the switching circuit unit in accordance with information abouta power status stored in a memory unit;

FIG. 6 shows a configuration of an image forming apparatus according toanother exemplary embodiment;

FIG. 7 shows an example of a mechanical switch provided in the imageforming apparatus according to another exemplary embodiment; and

FIGS. 8A and 8B are a flowchart showing a power control method of theimage forming apparatus according to an exemplary embodiment.

DETAILED DESCRIPTION

Below, exemplary embodiments will be described in detail with referenceto accompanying drawings.

FIG. 1 is a block diagram showing a configuration of an image formingapparatus according to an exemplary embodiment, and FIG. 2 is a circuitdiagram of a switching circuit unit according to an exemplaryembodiment.

An image forming apparatus 100 in this embodiment may be embodied by aprinter, a copy machine, a facsimile, a multi-function peripheral havingtwo or more functions, etc.

As shown in FIG. 1, the image forming apparatus 100 includes an imageforming unit 110 which forms an image on a printing medium, a powersupply 120 which supplies operating power to each component of the imageforming apparatus 100, a key input unit 130 which receives input about“on/off” of the operating power from a user, a switching circuit unit140 which performs a switching operation to selectively supply theoperating power, a controller 150 which controls the switching operationof the switching circuit unit 140 in accordance with information about apower status stored in a memory unit 160 when being supplied with power,the memory unit 160 which stores the information about the power statusof the switching circuit unit 140, a storage unit 170 which storesprinting data, and a communication interface unit 180 which communicatesdata with the exterior such as a host device. The image formingapparatus 100 may further include a random access memory (RAM) 151 and aread only memory (ROM) 152 needed for operation of the controller 150.

Also, the image forming apparatus 100 may include an additionalconfiguration such as a user interface (not shown) having a display forreceiving a user input and displaying an operation status, an imagescanner (not shown) scanning a document, and a fax unit (e.g., a modembut not shown) converting an image generated by the image scanner into afax signal and transmitting it to an external facsimile through a publicswitched telephone network (PSTN) or receiving a fax signal from theexterior, etc.

The image forming unit 110 forms an image to be printed on at least oneprinting medium (paper) on the basis of printing data if there is aprinting command. Here, the printing includes printing for copying afterscanning a document, printing of received fax data, and printing ofprinting data stored in the interior (e.g., a hard disk drive) or theexterior (e.g., a universal serial bus (USB) memory) of the imageforming apparatus 100 or received from the exterior through a hostdevice 300 including a server. In this exemplary embodiment, the imageforming unit 110 includes a developing unit having an image carryingbody, an optical scanning unit, a transfer unit and a fixing unit.

Examples of the image forming apparatus 100 in this exemplary embodimentincludes a monochromatic image forming apparatus using one developer(generally, black) to form an image, a color image forming apparatususing four developers to form a color image, and a multi-color imageforming apparatus using an auxiliary developer such as a white developerbesides the four developers to form a color image.

The power supply 120 supplies the operating power to each component ofthe image forming apparatus 100. As shown in FIG. 2, the power supply120 converts external alternating current (AC) power to direct current(DC) power, and supplies it to the switching circuit unit 140.

The key input unit 130 receives a user input about the supply of theoperating power.

FIG. 3 shows an example of the key input unit 130 provided in the imageforming apparatus according to an exemplary embodiment.

Referring to FIG. 3, the key input unit 130 is a soft power buttonprovided on a front side of the image forming apparatus 100, whichbecomes on/off in sequence in response to a user input. The key inputunit 130 is placed on the front side of the apparatus for theconvenience of a user.

If the key input unit 130 becomes (turns) on/off in accordance with auser input, a first switch PW_SW of the switching circuit unit 140 to bedescribed later is also turned on/off.

The switching circuit unit 140 performs the switching operation toselectively supply the operating power from the power supply 120.

As shown in FIG. 2, the switching circuit unit 140 includes the firstswitch PW_SW turned on in response to a user input into the key inputunit 130, and a second switch Q2 turned on/off in response to a powercontrol signal of the controller 150.

Here, the switching circuit unit 140 is a secondary circuit thatreceives the DC power, at least a part of which receives standby powerfor preventing data loss or part damage even in a power-off status. Forexample, the standby power is supplied to the first switch PW_SW, acapacitor C1, a transistor Q1, and resistors R1, R2, R3, R4, R5 and R7even in the power-off status.

Since the switching circuit unit 140 is configured with small-capacitydevices, the applied standby power is maintained at 1 W or less.

The controller 150 receives the operating power from the power supply120 through the switching circuit unit 140, and outputs a power controlsignal for controlling the switching operation of the switching circuitunit 140 to correspond to the power status information stored in thememory unit 160 when receiving power. Also, the controller 150 recordsthe information about the power status of the memory unit 160 inresponse to a user input of the key input unit 130 when the power issupplied to the image forming apparatus 100.

The controller 150 may be achieved by a central processing unit (CPU)that controls general operation of the image forming apparatus 100.

The memory unit 160 stores information about the power status of theswitching circuit unit 140. Specifically, if power is normally appliedin response to a user input of the key input unit 130, the controller150 records the information about the power status as “on” in the memoryunit 160.

If a user inputs a power-off command by operating the key input unit 130in the state that the information about the power status is stored as“on” in the memory unit 160, the controller 150 controls the informationabout the power status of the memory unit 160 to be changed into “off”and then recorded, and turns off the image forming apparatus 100.

Here, if power becomes off by an unexpected situation such as a powerfailure in the state that the information about the power status isstored as “on” in the memory unit 160, the image forming apparatus 100is turned off while keeping the information about the power statusstored as “on” in the memory 160.

The memory unit 160 is achieved by a non-volatile memory, and thenon-volatile memory is internally provided with a buffer for storing theinformation about the power status.

The storage unit 170 may further store various information such asvarious setup values of the image forming apparatus 100, fax data, ascan image generated by the image scanner, user registration informationset up according to user accounts, user authentication information, userright information, etc.

If a power-off command is input through the key input unit 130 or thepower supplied from the power supply 120 is shut off, the controller 150backs up data, with which the image forming apparatus 100 is operating,in the storage unit 170.

The storage unit 170 includes an internal storage medium such as a harddisk drive (HDD), or an external or portable storage medium such as aUSB memory, a memory card (e.g., a memory stick, a compact flash (CF)card, multi-media card (MMC)), etc.

In the image forming apparatus 100 according to this exemplaryembodiment, a separate memory unit 160 is provided for recording theinformation about the power status for enhancing a processing speed, butnot limited thereto. Alternatively, the information about the powerstatus may be stored in the storage unit 170 in order to decreaseproduction costs.

The communication interface unit 180 communicates data with an externaldevice including the host device. The communication interface unit 180may include a wired/wireless communication module connectable to theexternal device via a network based on a predetermined protocol, or acommunication interface such as a universal asynchronous receivertransmitter (UART) or a universal serial bus (USB).

Referring to FIG. 2, if power is supplied to the switching circuit unit140, the capacitor C1 connected to the first switch PW_SW is chargedwith electricity, and an electric current increases in a base of atransistor Q1 connected to the capacitor C1, so that the transistor Q1can be turned on. The power is also supplied to the controller 150, sothat the controller 150 is booted up and performs operation. Here, thesupply of power may include not only a normal case of supplying power inresponse to a user input into the key input unit 130, but also a case ofresuming the supply of power after the power is abnormally shut off byan unexpected factor such as a power failure.

If the capacitor C1 is continuously charged with electricity, theelectric current in the base of the transistor Q1 gradually decreases sothat the transistor Q1 can be turned off, which equivalently acts as ifthe first switch PW-SW is pressed for a predetermined time.

Here, a time constant based on the capacitor C1 and the resistor isdetermined to keep an “on” status of the transistor Q1 until thecontroller 150 transmits a control command for turning on a secondswitch Q2 through a general purpose output (GPO) port.

The controller 150 determines whether to turn on/off the first switchPW_SW through a general purpose input (GPI) port connected to the firstswitch PW_SW.

That is, if the supply of power is based on a user input into the keyinput unit 130, information about “on” is transmitted to the controller150 through the GPI port because the first switch PW_SW is in an “on”status.

On the other hand, if the supply of power is regardless of the userinput into the key input unit 130 (e.g., if the supply of power isresumed after the power failure), information about “off” is transmittedto the controller 150 since the first switch PW_SW is in an “off”status.

When the first switch PW_SW is in the “on” status, it is determined thatpower becomes on by a user's operation of the key input unit 130 so thatthe controller 150 can record the information about the power status as“on” regardless of the information about the power status stored in thememory unit 160.

Then, the controller 150 normally boots up and initializes the imageforming apparatus 100 and performs operation.

When the first switch PW_SW is in the “off” status, it is determinedthat power becomes on without a user's operation of the key input unit130 and the supply of power is resumed after power is shut off by apower failure or the like. Thus, the controller 150 reads theinformation about the power status stored in the memory unit 160.

Here, if the information about the power status stored in the memoryunit 160 is “off”, it may be determined that power is temporarily shutoff and then standby power is supplied again to the switching circuitunit 140 in a normal power-off status.

Thus, the controller 150 determines a last power status just beforebeing turned off as “off” and outputs a control signal for turning offthe second switch Q2 through the GPO port. If the second switch Q2 isturned off, the image forming apparatus 100 is also turned off and thusterminates all operations.

If the information about the power status stored in the memory unit 160is “on”, it may be determined that the supply of power is resumed afterthe power is abnormally shut off by a power failure or the like whilethe image forming apparatus 100 is in the power-on status.

Thus, the controller 150 determines the last power status just beforebeing turned off as “on”, so that the image forming apparatus 100 can benormally booted up and initialized and perform operations.

In addition, the controller 150 continuously monitors whether there is auser input into the key input unit 130 while the image forming apparatus100 is turned on and normally performs the operation.

That is, the controller 150 continuously checks a signal GPI_PowerButtonabout the first switch PW_SW, received through the GPI port.

If the first switch PW_SW is turned on, the controller 150 determinesthat a user handles the key input unit 130 to turn off the image formingapparatus 100, and records the information about the power status as“off” in the memory unit 160.

Further, the controller 150 controls the storage unit 170 to back upprinting data, with which the image forming apparatus 100 is working, orsystem data needed for operating the image forming apparatus 100, andoutputs a control signal for turning off the second switch Q2 throughthe GPO port when the backup is completed. When the second switch Q2 isturned off, the image forming apparatus 100 is also turned off andterminates all operations. Thus, the last power status stored in thememory unit 160 is “off”.

FIGS. 4 and 5 are graphs showing operation waveforms detected in eachnode of the switching circuit unit 140 in accordance with informationabout the power status stored in the memory unit 160.

The supply of power in FIGS. 4 and 5 corresponds to the case where thesupply of power is resumed after the power is abnormally shut off by thepower failure or the like regardless of a user's operation of the keyinput unit 130.

FIG. 4 illustrate that the power status is stored as “on” in the memoryunit 160.

As shown in FIG. 4, a high signal is detected in a node a as power issupplied, and a signal in a node b is gradually lowered from high as thecapacitor C1 is charged with electricity.

Since the power is supplied without operating the first switch PW_SW, asignal in a node c is maintained in a low status.

The controller 150 recognizes that the power is supplied withoutoperating the first switch PW_SW on the basis of the signal in the nodec input through the GPI port, and reads the information about the lastpower status stored in the memory unit 160.

In the case of the exemplary embodiment shown in FIG. 4, because thelast power status is stored as “on” in the memory unit 160, thecontroller 150 outputs a high signal so that the second switch Q2 can bemaintained in the “on” status, like a signal of a node d output throughthe GPO port.

Thus, the signal finally input to the second switch Q2 is a power-onsignal, like a node e.

Then, the controller 150 monitors whether there is a user input into thekey input unit 130, senses that the “on” status of the first switchPW_SW through the GPI port like the signal of the node c, and outputs acontrol signal for power-off by turning off the second switch Q2 throughthe GPO port.

In succession, if receiving an “on” signal of the first switch PW_SWthrough the GPI port through the power off status, the controller 150outputs a control signal for power-on by turning on the second switch Q2through the GPO port.

FIG. 5 illustrate that the power status is stored as “off” in the memoryunit 160.

As shown in FIG. 5, a high signal is detected in a node a as power issupplied, and a signal in a node b is gradually lowered from high as thecapacitor C1 is charged with electricity.

Since the power is supplied without operating the first switch PW_SW, asignal in a node c is maintained in a low status.

The controller 150 recognizes that the power is supplied withoutoperating the first switch PW_SW on the basis of the signal in the nodec input through the GPI port, and reads the information about the lastpower status stored in the memory unit 160.

In the case of the exemplary embodiment shown in FIG. 5, because thelast power status is stored as “off” in the memory unit 160, thecontroller 150 changes the high signal into a low signal and outputs itso that the second switch Q2 can be changed into the “off” status, likea signal of a node d output through the GPO port.

Thus, the power is supplied only in a section where the signal of thenode d is high, and the signal finally input to the second switch Q2 isa power-off signal, like a node e.

Then, the controller 150 monitors whether there is a user input in thekey input unit 130, senses that the “on” status of the first switchPW_SW through the GPI port like the signal of the node c, and outputs acontrol signal for power-off by turning off the second switch Q2 throughthe GPO port.

Referring to FIGS. 4 and 5, it can be appreciated that the signal inputto the node a indicates that the standby power is continuously receivedexcept the case where the power is shut off by an abnormal situation andthen supplied again.

FIG. 6 shows a configuration of an image forming apparatus 100 accordingto another exemplary embodiment.

As compared with the image forming apparatus 100 according to theforegoing exemplary embodiment, the image forming apparatus 100 in thisexemplary embodiment shown in FIG. 6 further includes a mechanicalswitch 190 before a stage where the power supply 120 receives externalpower. Here, if the standby power exceeds a predetermined standard(e.g., 0.1 W, 0.5 W, 1 W, etc.) individually provided according tocountries when the switching circuit unit 140 is turned off, the imageforming apparatus 100 may include a separate mechanical switch 190.

Typically, there may be no need of the mechanical switch 190 if powerconsumption in a standby mode is 0.1 W or less (Korean standards) or 0.5W or less (Environmental Protection Agency (EPA) standards). However,even though the image forming apparatus 100 satisfies the standards ofthe standby power, the separate mechanical switch 190 may be provided inthe image forming apparatus 100 by taking safety of a product intoaccount.

With regard to other elements than the mechanical switch 190, the samenumerals and terms will be used, and repetitive descriptions will beavoided.

FIG. 7 shows an example of the mechanical switch 190 provided in theimage forming apparatus 100 according to another exemplary embodiment.

As shown in FIG. 7, the mechanical switch 190 is placed in the vicinityof a connector 191 for receiving external power (e.g., in a back side ofthe image forming apparatus 100), and completely shuts off AC powersupplied from the exterior to the image forming apparatus 100.

The switching circuit unit 140 and the controller 150 in this exemplaryembodiment operate equally to those of the foregoing exemplaryembodiment, and the same waveforms as those of FIGS. 4 and 5 aredetected.

In this exemplary embodiment, the case where the power is abnormallyshut off regardless of a user's operation of the key input unit 130 andsupplied again includes not only the power failure but also a case wherea user turns off the mechanical switch 190 and then turn it on again inthe state that power (including the standby power) is supplied to theswitching circuit unit 140 of the image forming apparatus 100.

The image forming apparatus 100 in this exemplary embodiment may furtherinclude a power saving button (not shown) for entering a power savingmode (Hereinafter, referred to as a “sleep mode”) or returning from thepower saving mode to the standby mode, i.e., switching into a wake-upstate.

The image forming apparatus 100 may enter the power saving mode if apreset time (e.g., 1 minute, 5 minutes, 10 minutes, 15 minutes, 30minutes, 1 hours, etc.) is elapsed in the state that a printingoperation is not being performed, or if there is a user input in thepower saving button.

In the case of the image forming apparatus 100 having no separate powersaving button, if a user input is detected corresponding to a soft powerbutton, i.e., in the key input unit 130, a user is asked to selectpower-off or power-save (i.e., entering the power saving mode) and thusthe image forming apparatus 100 may enter the power saving mode inaccordance with a user's response. Also, if the key input unit 130 ishandled for a predetermined period of time (e.g., for 2.5 seconds) inthe power saving mode, the image forming apparatus 100 may be poweredoff.

In the power saving mode, power is not supplied to a liquid crystaldisplay (LCD) window provided as a user interface, and only key inputscorresponding to the soft power button and the power save button arerecognizable, so that the image forming apparatus 100 can be waken up inresponse to a key input corresponding to the soft power button and thepower save button.

Also, the image forming apparatus 100 may be waken up not only by thekey input corresponding to the soft power button and the power savebutton in the power saving mode, but also by operating an optionaldevice such as sensing a printing command through the USB or awired/wireless network, receiving a fax, opening/closing a cover forreplacing a developer or the like, scanning, etc.

In the image forming apparatus with the foregoing configurations, apower control method thereof will be described with respect to FIGS. 8Aand 8B.

FIGS. 8A and 8B are a flowchart showing a power control method of theimage forming apparatus according to an exemplary embodiment.

As shown in FIG. 8A, at operation S202, power may be supplied from thepower supply 120 to the switching circuit unit 140 in the state that theimage forming apparatus 100 is in the power-off status. Here, the supplyof power may include supply of power in response to a user input intothe key input unit 130; resumed supply of power after a power failure;supply of power by turning off the mechanical switch 190 and thenturning it on again according to another exemplary embodiment; etc.

In the operation S202, if the image forming apparatus 100 receives thepower, the controller 150 is booted up and thus a power-on controlsignal is output through the GPO port, thereby turning on the secondswitch Q2 of the switching circuit unit 140 at operation S204.

At operation S206, the controller 150 checks whether there is an inputinto the key input unit 130 with regard to the supply of power in theoperation 202 on the basis of the signal input through the GPI port.

Specifically, the controller 150 determines whether the first switchPW_SW is in the “on” status or not at operation S208. That is, the firstswitch PW_SW is in the “on” status if the supply of power is based onthe input into the key input unit 130, but the first switch PW_SW is inthe “off” status if the supply of power is based on operating thephysical switch 190 after a power failure. The controller 150 candetermine whether the first switch PW_SW is in the on/off status on thebasis of the signal input through the GPI port.

In the operation S208, if it is determined that the first switch PW_SWis in the “on” status, the supply of power is based on a user'soperation of the key input unit 130 in the operation S202. Thus, atoperation S210, the controller 150 records the information about thepower status as “on” in the memory 160 regardless of the informationabout the last power status previously stored in the memory unit 160.

In the operation S208, if it is determined that the first switch PW_SWis in the “off” status, the supply of power is regardless of a userinput into the key input unit 130 in the operation S202. Thus, atoperation S212, the controller 150 reads information about the lastpower status stored in the memory unit 160.

If the information about the power status read in the operation S212 is“off”, this corresponds to a case where the power supplied from theexterior is temporarily shut off and then supplied again in the “off”status of the switching circuit unit 140, i.e., while receiving only thestandby power, and therefore the controller 150 outputs a control signalfor turning off the second switch Q2 through the GPO port and theswitching circuit unit 140 is turned off at operation S216.

If the information about the power status read in the operation S212 is“on”, this corresponds to abnormal power shut-off (e.g., a powerfailure, turned-off of the mechanical switch 190, etc.) in the statethat power is supplied to each element of the image forming apparatus100, and therefore the controller 150 initializes the image formingapparatus 100 at operation S218.

As shown in FIG. 8B, if the initialization in the operation S218 iscompleted, the image forming apparatus 100 performs its own operationsnormally at operation S220.

In the state that the image forming apparatus 100 is turned on andnormally performs the operations, the controller 150 continuouslymonitors whether there is a user input through the key input unit 130 atoperation S222.

At operation S224, the controller 150 determines whether a user inputfor power-off is received into the key input unit 130 on the basis ofthe monitoring in the operation S222. Here, the controller 150 detectswhether the first switch PW_SW is turned on as a user input into the keyinput unit 130, thereby determining whether there is the user input.

If it is detected that the first switch PW_SW is turned on in theoperation S224, this corresponds to a case where the user input forpower-off is received input the key input unit 130, and therefore thecontroller 150 records the information about the power status as “off”in the memory unit 160 at operation S226.

Further, the controller 150 controls the storage unit 170 to back upvarious data related to operations of the image forming apparatus 100 atoperation S228.

If the data is completely backed up in the operation S228, thecontroller 150 outputs a control signal for turning off the secondswitch Q2 through the GPO port, and thus the switching circuit unit 140is turned off at the operation S216.

If the switching circuit unit 140 is turned off in the operation S216,power is not supplied to the image forming apparatus 100 including theimage forming unit 110, the controller 150, the RAM 151, the ROM 152,the memory unit 160, the storage unit 170 and the communicationinterface unit 180, but supplied to only at least a part of theswitching circuit unit 140 configured with a small capacity device,thereby keeping the standby power of 1 W or less.

Accordingly, power control is possible by not the mechanical switch 190but the switching circuit unit 140 turning on/off the DC power of thesecondary circuit, and operation based on the last power status ispossible when power is supplied again after unexpected power shut-off,thereby enhancing reliability of the image forming apparatus 100.

The switching circuit unit 140 according to an exemplary embodimentemploys a small-capacity device to configure the secondary circuit forcontrolling the power without increasing costs due to the MICOM or thelike, and may use a 24-hours timer or the like for controlling thepower, thereby improving a user's convenience.

As apparent from the above description, there are provided an imageforming apparatus and a power control method thereof, in which if theimage forming apparatus is turned off by unexpected power-off such as apower failure and then resumed, a power status previously stored justbefore the power-off is ascertained to make the image forming apparatusoperate in a last power status, thereby preventing power from beingwastefully consumed or data from being lost.

Also, a microcomputer (MICOM) is not additionally needed for powercontrol, thereby saving costs on production.

Further, the stability of the image forming apparatus can be moreenhanced while keeping a standby power of 1 W or less irrespective ofpresence of a mechanical switch.

Although a few exemplary embodiments have been shown and described, itwill be appreciated by those skilled in the art that changes may be madein these exemplary embodiments without departing from the principles andspirit of the disclosure, the scope of which is defined in the appendedclaims and their equivalents.

1. An image forming apparatus comprising: an image forming unit whichforms an image; a power supply which supplies operating power for theimage forming apparatus; a switching circuit unit which switches toselectively supply the operating power; a memory unit which storesinformation about power status of the switching circuit unit; and acontroller which outputs a power control signal to control a switchingoperation of the switching circuit unit in accordance with theinformation about the power status stored in the memory unit if power isabnormally shut off and then supplied again from the power supply to theswitching circuit unit.
 2. The image forming apparatus according toclaim 1, further comprising a key input unit through which a user inputrelated to supply of the operating power is received, wherein theswitching circuit unit comprises a first switch turned on in response tothe user input into the key input unit, and a second switch turnedon/off in response to the power control signal of the controller, andthe controller reads the information about the power status from thememory unit and outputs the power control signal for turning on/off thesecond switch to match with the read information about the power statusif power is supplied to the switching circuit unit without a user inputto the first switch.
 3. The image forming apparatus according to claim2, wherein the controller initializes the image forming apparatus andmonitors the user input to the first switch if the read informationabout the power status is “on”.
 4. The image forming apparatus accordingto claim 3, the controller records the power status of the switchingcircuit unit as “off” in the memory unit and controls the switchingcircuit unit to shut off the operating power if the user input to thefirst switch is received.
 5. The image forming apparatus according toclaim 4, wherein the controller backs up data of the image formingapparatus, and controls the switching circuit unit to shut off theoperating power.
 6. The image forming apparatus according to claim 2,wherein the controller outputs a power control signal for turning offthe switching circuit unit if the read information about the powerstatus is “off”.
 7. The image forming apparatus according to claim 2,wherein the controller records the power status of the switching circuitunit as “on” in the memory unit if power is supplied to the switchingcircuit by the user input to the first switch.
 8. The image formingapparatus according to claim 7, wherein the controller initializes theimage forming apparatus, and monitors the user input to the firstswitch.
 9. The image forming apparatus according to claim 8, wherein thecontroller records the power status of the switching circuit unit as“off” in the memory unit if receiving the user input to the firstswitch, and controls the switching circuit unit to shut off theoperating power.
 10. The image forming apparatus according to claim 9,wherein the controller backs up data of the image forming apparatus, andcontrols the switching circuit unit to shut off the operating power. 11.The image forming apparatus according to claim 1, wherein the memoryunit comprises a non-volatile memory.
 12. A power control method of animage forming apparatus comprising a power supply for supplyingoperating power, and a switching circuit unit for switching toselectively supply the operating power, the power control methodcomprising: supplying power from the power supply to the switchingcircuit unit; reading information about power status from a memory unitstoring information about power status of the switching circuit unit ifpower is abnormally shut off and then supplied again to the switchingcircuit unit; and outputting a power control signal for controlling aswitching operation of the switching circuit unit in response to theread information about the power status.
 13. The power control methodaccording to claim 12, wherein the switching circuit unit comprises afirst switch turned on in response to a user input related to supply ofthe operating power, and a second switch turned on/off in response tothe power control signal of the controller, and if power is supplied tothe switching circuit unit without the user input to the first switch,the outputting of the power control signal comprises outputting thepower control signal for turning on/off the second switch to match withthe read information about the power status.
 14. The power controlmethod according to claim 12, further comprising initializing the imageforming apparatus; and monitoring a user input to a first switch of theswitching circuit unit, if the read information about the power statusis “on”.
 15. The power control method according to claim 14, furthercomprising receiving the user input to the first switch; recording thepower status of the switching circuit unit as “off” in the memory unit;and outputting the power control signal to shut off the operating power.16. The power control method according to claim 15, further comprisingbacking up data of the image forming apparatus.
 17. The power controlmethod according to claim 12, wherein the outputting of the powercontrol signal comprises outputting the power control signal for turningoff the switching circuit unit if the read information about the powerstatus is “off”.
 18. The power control method according to claim 13,further comprising recording the power status of the switching circuitunit as “on” in the memory unit if power is supplied to the switchingcircuit unit by the user input to the first switch.
 19. The powercontrol method according to claim 18, further comprising initializingthe image forming apparatus; and monitoring the user input to the firstswitch.
 20. The power control method according to claim 19, furthercomprising recording the power status of the switching circuit unit as“off” in the memory unit if receiving the user input to the first switchto shut off the operation power as a monitoring result; and controllingthe switching circuit unit to shut off the operating power.
 21. Thepower control method according to claim 20, further comprising backingup data of the image forming apparatus.
 22. The power control methodaccording to claim 12, wherein the memory unit comprises a non-volatilememory.
 23. A power control method of an image forming apparatuscomprising a power supply to supply operating power, a key input unitfor receiving a user input related to supply of the operating power, anda switching circuit unit for switching to selectively supply theoperating power, the power control method comprising: supplying powerfrom the power supply to the switching circuit unit; recording a powerstatus of the switching circuit unit as “on” in the memory unit if poweris supplied to the switching circuit unit because the key input unitreceives the user input requesting that power be supplied from the powersupply to the switching circuit unit; and initializing the image formingapparatus.
 24. The power control method according to claim 23, furthercomprising supplying power to a controller as the power is supplied tothe switching circuit unit, and booting up the controller, wherein theimage forming apparatus is initialized by the booted-up controller. 25.The power control method according to claim 23, further comprisingmonitoring the user input to the key input unit; recording the powerstatus of the switching circuit unit as “off” in the memory unit ifreceiving the user input to the first switch to shut off the operatingpower as a monitoring result; and outputting a power control signal toshut off the operating power.
 26. The power control method according toclaim 25, further comprising backing up data of the image formingapparatus.